1. Field of the Invention
The present invention relates generally to laser photoablation, and more specifically to non-contact laser photoablation methods and systems that apply cluster analysis to photoacoustic signals for recognizing tissue compositions during a photoablation procedure.
2. Description of the Related Art
Today, it takes a highly skilled, and specially trained surgeon, with nearly a million U.S. dollars worth of equipment, to perform complicated vision corrective procedures. However, these procedures are only as good as the surgeon""s ability to visualize distinctions between different types of corneal tissue. For instance, the doctor must use his own eyesight to see the changes occurring in the patient""s tissues occurring during the surgery. Consequently, during a photoablation procedure, while the doctor is removing tissue layers of sub-micron size, it is not possible for the surgeon to visualize the microscopic, delicate changes taking place in the tissue.
A well known form of vision corrective surgery removes a precise amount of tissue from the center of the cornea by utilizing a computer program. The program calculates the precise amount of tissue to be removed by laser vaporization. However, this method does not provide information as to the type of tissue being removed or guidance as to completion of the removal process. As a result, a generic amount of tissue is removed without addressing the specificity of the tissue. Moreover, the uniqueness of each individual is not addressed including the fact that a certain amount of tissue removal in one patient may be beneficial but ineffective and/or detrimental in another patient.
Accordingly, at the present time, a compelling need exists in the art for a photoablation method that discriminates and differentiates between tissues, such as determining corneal epithelium from stroma tissue or healthy tissue from diseased tissue; provides a visual output signal that is representative of the specific tissue being removed; determines the ablation rate; and alerts the surgeon of an approaching interface between tissue to be removed and tissue to be retained, thereby increasing specificity and precision of the photoablation procedure.
The present invention generally relates to laser photoablation, and more specifically to a method and system for photoablation by impinging multiple pulses of electromagnetic energy onto target tissue to ablate and generate an acoustic pressure wave while concurrently processing signals produced by the acoustic pressure wave. A cluster analysis algorithm may be used to process the generated signals, and as a result, a representative pattern can be provided to guide the surgeon through distinct tissue layers.
The invention, as described hereinafter in greater detail, contemplates in various aspects:
a laser photoablation method that differentiates between distinct tissue layers;
a laser photoablation method and system that together provides a visual signal representative of the specific tissue being removed;
a laser photoablation system that alerts the surgeon of an imminent approach of an interface between removed and retained tissue;
a laser photoablation method that reduces damage to surrounding tissue thereby providing for faster recovering of the patient, increasing success rates of corrective procedures and minimizing risks relating to the surgery; and
a laser photoablation method that increases the specificity and precision of a photoablation procedure.
In one specific aspect, the invention relates to a guided non-contact tissue ablation method controllably mediated by recognition of distinct tissue composition within a volume of tissue, the method comprising:
a) impinging multiple pulses of electromagnetic energy onto the tissue to ablate impinged tissue and generate an acoustic pressure wave in response to interaction of the tissue with the electromagnetic energy;
b) non-contactingly sensing the generated acoustic pressure wave and providing a plurality of corresponding signals;
c) processing the signals by applying thereto a cluster analysis algorithm to recognize distinct tissue composition.
The method may further comprise generating a representative pattern of the impinged tissue to recognize distinct layers of tissue composition.
In another aspect, the invention relates to a guided non-contact tissue ablation system that is controllably mediated by recognition of distinct types of tissue composition, the system comprising:
a) at least one electromagnetic energy source for generating multiple pulses of electromagnetic energy to ablate impinged tissue and generate an acoustic pressure wave;
b) at least one non-contacting sensing means for sensing the acoustic pressure wave and providing a plurality of corresponding signals and
c) at least one processing means for analyzing the signals of the acoustic pressure wave by a cluster analysis algorithm to recognize distinct tissue composition.
In yet another aspect, the invention relates to a non-contact tissue ablation method controllably mediated by recognition of tissue composition, the method comprising:
a) impinging multiple pulses of electromagnetic energy onto at least one location of the tissue to ablate impinged tissue and to generate at least one acoustic pressure wave in response the electromagnetic energy impinging the tissue;
b) non-contactingly sensing the at least one generated acoustic pressure wave to provide a plurality of corresponding signals; and
c) processing the plurality of signals by analyzing a property of the signal to determine change in the ablated tissue.
The signal, formed by the generated acoustic wave, has multiple properties that can be examined and analyzed to provide information concerning location of impingement, change in the ablated tissue type, and changes in the tissue due to interference of acoustic waves. The properties of the emitted signal may include, the frequency, velocity, wavelength, phase of the acoustic wave and the like. If multiple locations are impinged with electromagnetic energy, responses within the tissue, caused by the generated acoustic wave, may be superimposed causing either constructive or destructive interference. This point of interference may be located by implementing triangulation calculations.
Other aspects, features and embodiments of the invention will be more fully apparent from the ensuing disclosure and appended claims.